Technical Field
This invention relates to bacterial therapy for the treatment of cancer. In particular, the invention is highly customized “designer” strains of enhanced cancer cell-targeting bacteria for individualized cancer therapy, their method of creation, and their use in the treatment of human patients with cancer.
State of the Art
For at least three hundred years, those tending to the sick have occasionally observed regression of cancerous tumors in people suffering from severe acute infectious illnesses. At times, when the afflicted person survived an adequately severe and lengthy infection, the cancer completely disappeared resulting in a cure. In the late 19th and early 20th centuries, William B. Coley, a New York oncologist, infected cancer patients with Streptococcus pyrogenes or administered extracts of the bacteria deemed “Coley's toxins, reportedly with remarkable results. (Hoffman, R. Bugging tumors. Cancer Discovery Jul. 11, 2012; p. 588.)
This phenomenon was largely ignored after Cooley's death in 1936, but interest in this unique form of cancer treatment has recently increased. The very conditions which make cancerous tumors resistant to conventional chemotherapy—an acidic pH microenvironment resulting from hypoxia and tumor necrosis—are favorable for the growth of anaerobic bacteria. Various genera of anaerobic bacteria, most notably Clostridium and Bifidobacterium, selectively infect necrotic regions of tumors over healthy tissue. But because these obligate anaerobes cannot establish infection in a non-hypoxic microenvironment, therapy with anaerobic bacteria must be combined with chemotherapy to kill viable solid tumors, small metastatic deposits, and individual cancer cells. Accordingly, Salmonella, a facultative anaerobe that exhibits sustained growth in both viable and necrotic regions of a tumor, has been shown to infect cancerous tumors, killing cancer cells in all regions of the tumor. Tumoricidal activity has also been noted in other genera of facultative anaerobes, such as Streptococcus and Escherichia. 
To be an effective cancer treatment in vivo, a bacterial strain must not only be sufficiently cytotoxic to kill the cancer cells, but also unable to sustain an infection in normal tissues causing severe illness or death. Strategies employed to increase safety center around inducing mutations in wild-type bacteria, and then selecting for the mutated desired traits. Mutations decreasing the virulence of bacteria by altering the organism's ability to express cytotoxic characteristics, such as gene-based chemical changes of the wild-type lipopolysaccharide (“LPS”) resulting in an attenuated host cytokine response are described. Also described are creating mutated strains auxotrophic for one or more nutrients, including purines and/or amino acids.
S. typhimuruim is a facultative anaerobe which can mount a sustained infection in both healthy and necrotic tissue. A strain of S. typhimurium auxotrophic for both arginine and leucine has been developed. Mutagenesis of a wild population of Salmonella typhimuruim is induced using nitrosoguanidine (“NTG”), and a resulting dual auxotroph for the amino acids leucine and arginine (“Leu-Arg”) is selected from the heterogeneous population of auxotrophs, non-auxotroph mutations, and non-mutated wild bacteria. This Leu-Arg dual auxotroph (S. typhimuruim A1, or “A1”) is unable to sustain an infection within somatic cells or normal tissue, but grows actively in individual cancer cells and malignant tumors. Otherwise, A1 has no other attenuating mutations limiting its cytotoxicity in infected tissues. S. typhimurium, therefore, has therapeutic potential. (Hoffman, R. Bugging tumors. Cancer Discovery Jul. 11, 2012; p. 588.)
Ideally, a bacterial strain 100% specific for the cancer of interest that is completely non-toxic to the host/patient is needed, along with a simple reproducible method for creating and using this strain in the treatment of human patients with cancer. No such strain exists in the prior art that even approaches this ideal, nor does a straightforward and reproducible method for producing such a strain.
Citation of documents herein is not an admission by the applicant that any is pertinent prior art. Stated dates or representation of the contents of any document is based on the information available to the applicant and does not constitute any admission of the correctness of the dates or contents of any document.